I brought my scooter to WDW twice last year. First time on United Airlines direct flight from Los Angeles. They didn't load the scooter and had to send it on the next flight out. It was sent right to the hotel. (United paid for a one day rental).
Second trip bringing my scooter was this past August. Flying Southwest from Los Angeles with a plane change. I was able to drive my scooter down the jetway and they had an elevator to take the scooter down from the jetway. Changing planes, I just sent the scooter to the connecting flight and they had a wheelchair waiting for me at the gate. The scooter arrive when I did
We went to ME and waited a lift bus. They had a regular bus waiting and they put the scooter below the bus. It worked out just fine. On the return to MCO, the scooter went under the bus again. They wouldn't let me use a lift with the scooter. Was told it is for wheelchairs only, mainly because of how much longer the scooter is vs the wheelchair. Don't know if that is true, but that is what I was told.
You should have no problems with ME. Be cautious of how the airlines handle the equipment. Will be flying Southwest again next time.